Protective- relaying equipment



Sept. 1942- E. L. HARDER Re. 22,179

PROTECTIVE RELAYING EQUIPMENT Original F iled Nov. 12, 1958 2 Sheets-Sheet l W- -W g zfg :66

19. 1' (e) JAG/r/lf h bo-re a-y) WITNESSES: 0 INVENTOR fi L b w/riLf/oraafi QM. Wm

ATTORNEY Reissued Sept. 22, 1942 PROTECTIVE RELAYING EQUIiMENT Edwin L. Harder, Wilkinsburg, Pa., assignor to Westinghouse Electric & pany, East Pittsburgh, Pa.,

Pennsylvania.

Manufacturing Coma corporation of Original No. 2,242,951, dated May 20, 1941, Serial No. 239,916, November 12,

1938. Application for reissue January 3, 1942, Serial No. 425,578

32 Claims.

My invention relates to protective relaying equipment for three-phase electrical transmission lines or other electrical apparatus.

In recent times, considerable progress has been made in the replacement of moving contacts, in relaying circuits, by stationary networks which combine complicated electrical relations in a polyphase circuit, in order to produce a simple electrical quantity for operating a mechanically simple relay. These stationary networks have proven themselves to be beyond a doubt far more reliable than the use of several mechanical relays responsive separately to the several electrical quantities, and requiring high-speed coordinative action of their various contact-circuits.

One object of the present invention is the production of a single-element relaying device which is responsive to the distance of a faultfrom the relaying point, as measured along the transmission line, so as to respond to any one of a plurality of different kinds of faults.

A more specific object of my invention is to provide a combination of networks, with a single relaying device, utilizing the ratio of (Eli-E2) to (I1I2) as a very satisfactory, though not theoretically exact, single measure of thedistance to the fault, where E1 and 11, represent the positive phase-sequence line-voltage and linecurrent, respectively, and E2 and I2 represent the negative phase-sequence line-voltage and linecurrent, respectively, the bars over the symbols indicating absolute quantities.

Further objects of my invention relate to various circuits and expedients for utilizing the above-mentioned arbitrary discriminating quantity or ratio, and in particular, circuits utilizing derived relaying voltages responsive to the vector values of the various phase-sequence quantities I1, I2, E1 and E2, in combination wi th rectifiers for obtaining the absolute values I1, 12, E1 and E2 of the respective phase-sequence quantities, and a relaying circuit in which the various rectified voltages are connected in series-circuit relation to each other.

Further objects of my invention relate to the utilization of a mechanically simple relay in connection with a coupling means which energizes the relay in response to th absolute value In of th zero phase-sequence component of the line-current. This absolute zero-sequence value is preferably obtained, as above indicated, with the aid of a rectifying device, and it may be utilized either separately or in combination with the response to the previously mentioned ratio,

(Eh-E2) to (i1-i2).

With the foregoing and other objects in view, my invention consists in the circuits, apparatus, systems, combinations and methods hereinafter described and claimed, and illustrated in the accompanying drawings, wherein:

Figure 1 (a) is a single-line diagrammatic view of a typical three-phase transmission system to which my invention is applicable;

. Figs. 1 (b) to l (e) are voltage-diagrams illustrating the voltage-distribution along the line for different types of faults; and,

Fig. 2 is a diagrammatic view of circuits and apparatus embodying my invention in a preferred form.

Fig. 1 (a) illustrates a transmission or distribution network which is sufficiently general, in character, to illustrate any power system to which my invention is applied. This system is symbollically represented by two sources I and 2, separated by a certain distance from each other and connected by line-sections 3, 4, 5, B and I, with a parallel-connected line-section 8 illustrated as being connected in parallel to the line sections 4, 5 and 6. The power system represented in Fig. 1 is assumed to be a three-phase system, the three phases being indicated by a single line, in accordance with a known convention. It'is presumed that a fault occurs at the point marked X between the line-sections 5 and 6, and that the relaying station is at a circuit-breaker 9, at the junction between the line-sections 4 and 5, and disposed between the fault X and the source i. It will be assumed that the positive, negative and zero phases'equence line-currents I1, I2 and In are positive when flowing from the relaying point 9 to the fault X, as indicated by the arrow in Fig. 1. It will be further assumed that the corresponding phase-sequence impedance-components of the line-section 5 between the relaying point 9 and the fault X are Z1, Z2 and Z0.

In Fig. 1 (b), I consider the'case of a threephase fault, and I plot the distribution of the positive phase-sequence voltage E1, from the source I, where this voltage is indicated as E1 to the fault X, Where the positive phase-sequence voltage is designated by a prime, as E'i. In the case of a three-phase fault, there are no negative or zero-sequence currents or voltages. At the fault-point X, the positive-sequence voltage E1 is zero, neglecting faultimpedance as is customary for faults not involving-ground. At the relaying point 9, the positive-sequence voltage'is represented by the equation,

E1=I1Z1 (1) In the event of a three-phase fault, as indicated in the aforesaid Fig. 1 (b), as well as any other kind of fault, the positive-sequence lineimpedance Z1 is proportional to the distance to b the fault, so that a measure of this impedance will be a measure of the fault distance from the relaying point, giving the equation,

Z1=E1/I1 (2) In Fig. 1, (c), I consider the case of a line-toline fault, designated IL, on phase b-c, where phase-a. is considered at the principal phase of reference 'of the symmetrical components. In this case, the positive-sequence voltage, starting with the value Ei at the source, dwindles along the line, until it reaches a certain value E'1, at the fault, where it becomes, in effect, a source of negative-sequence voltage E'2, so that The negative-sequence voltages starts with the value Ef2 at the fault and dwindles, as we move back along the line, from the fault-point to the point of no voltage of negative sequence.

For all static equipment having three-phase balance, the positive and negative phase-sequence impedances Z1 and Z2 are the same, and we have the relationship,

Zi=Z2 (4) In the well-known phase-sequence analysis of a line-to-line fault, the positive and negative phase-sequence impedance-networks are connected in series, so that we have the relationship,

noting that the negative-sequence voltage-drop I2Z2 has the negative sign when measured from the fault-point X back to the relaying-point 9, because the currents are positive when measured from the relaying-point to the fault-point. Substituting from Equation 4, we have,

Z1: (E1E2)/(I1-I2) (7) Comparing Equations 7 and 2, it will be noted that Equation '7 is the more general, and that it also gives the correct value in case of a threephase fault, in which case E2 and I2 are both zero.

In my discussion of a line-to-line fault, in connection with Fig. 1(0), it is to be noted that the relationships represented by this figure are applicable only to a fault on phase bc, if phase-a is the reference-phase of the system of symmetrical coordinates. In this case, however, it follows, from Equations 4, 5 and 6, that the relayingpoint phase-sequence voltages E1 and E2 are very nearly in phase with each other for any practical power-system. Thus, it would not make an appreciable difference, in consideration of the order of magnitude of the accuracy which is necessary for relaying purposes, if we modified Equation 7 by utilizing absolute values instead of vector values of the various relaying quantities, in order to obtain an indication of the distance of the fault from the relaying point. Indicating these absolute values by bars placed over the quan- If, now, we utilize the absolute values, as indicated in Equation 8, and if we should assume that the lineto-line fault is on any phase other than phase b c, the phase-sequence currents and voltages I1, I2, E1 and E2 will be shifted by some forward and some backward, but their mag nitudes or absolute values will remain unchanged, as compared to the values which were obtained when the fault was on phase bc. It thus follows that Equation 8 is a sufficiently accurate measure of the fault-distance for a line-to-line fault, regardless of which phase is faulted.

In Fig. 1(d), I consider the case of a double line-to-ground fault, designated as 2L-G, assuming the fault to be on the phases b-cg. In this case, the positive-sequence fault-voltage E1 becomes the source of voltage for both the negative-sequence fault-voltage E'2 and the zerosequence fault-voltage E0, the latter two voltages being connected in parallel with each other in the well-known equivalent phase-sequence diagram.

The voltage-distribution diagram for the double line-to-ground fault, as shown in Fig. 1(d), is identical with that for a line-to-line fault, as shown in Fig. 1(c), except for the addition of the zero-sequence voltage E0, which is indicated in dotted lines in Fig. 1(d). This zero-sequence voltage starts with its maximum value Eo at the fault-point X, and reduces to zero at some point II], which, in general, is different from the location of the source I.

Since I utilize a relaying system which responds to only positive and negative-sequence quantities, according to Equation 8, the presence of a zero-sequence voltage EU and a zero-sequence current Io at the relaying point, in the case of double line-to-ground faults as shown in Fig. 1(d), will not have any effect upon the impedance-measurement, sequence impedance Z0, which is in parallel with the negative-sequence impedance Z2 in the wellknown equivalent-impedance diagram, will, in general, cause I2 and E2 to be out of phase with I1 and E1, respectively, in the true distancemeasuring Equation 7, causing Equation 8 to be very slightly inaccurate unless said phase-displacements reduce both the numerator and the denominator of Equation '7 in the same ratio.

In Fig. 1(e) I consider the case of a single lineto-ground fault, or what is commonly known simply as a ground-fault, designated at ILG. In this case the positive-sequence fault-voltage E'1 becomes the source of the negative-sequence fault-voltage E2 and the zero-sequence faultvoltage E'o, the latter two voltagesbeing considered as being connected in series with each other,. from the well-known equivalent phasesequence diagram, so that E1=E'2+E'u (9) from which it follows that the apparent distance to which the relay responds is given by except that the zero-.

A comparison of Equation 11 with Equation 8 will show that a relay which is energized so as to have abalance-point as defined in Equation 8, will indicate too great a line-to-fault impedance Z1 if the fault is a single line-to-ground fault in which the actual line-to-fault impedance is as indicated in Equation 11. In other words, a relay energized in accordance with Equation 8 will measure too much impedance, by reason of its failure to respond to the zero-sequence fault-voltage Eo. Another way of saying this, is that the relay will not reach out as far, in responding to single line-to-ground faults, or simply groundfaults, as in responding to any of the so-called phase-faults such as the three-phase faults, the line-to-line faults, and the double line-to-ground faults. An important thing to note about my relay, in accordance with Equation 8, is that it will not cause a faulty relaying operation by tripping too far, in the event of a ground-fault on the line.

Fig. 2 illustrates a specific form of embodiment of apparatus utilizing the principles of my invention. In this figure, the three-phase line-section is indicated by three line-conductors a, b and c and the three-phase circuit breaker 9 is represented as having a trip-coil l3. Line-current transformers It supply currents to a positivesequence network I1 and to a network-sequence network I2, for supplying relaying voltages which are responsive, respectively, to the positive-sequence line-current I1 and to the negative-sequence line-current I2.

The particular phase-sequence current-responsive networks I1 and 12, shown in Fig. 2, are similar to those which are described and claimed in a Lenehan application, Serial No. 187,510, filed January 28, 1938. These networks, as illustrated, each comprises two resistors R, connected in one of the phases, such as phase-a, and a three-coil mutual-impedance 7' /3R having one coil con nected in each of the phases b and c and having the third coil connected in the measuring circuit, or in series with the output-terminals of the network. Each network, as illustrated, also embodies two auxiliary current-transformers l5 and it, connected in phases b and 0, respectively, for circulating an additional current (Ib-l-Ie) through one of the resistors R. The response of the measuring-circuit or output-circuit of such a current-responsive phase-sequence network is rep resented in the form of a voltage as follows:

Em=6RI1 (13) The negative-sequence current-responsive net- Work I2 has a response corresponding to the negative sign of the imaginary term of Equation 12, producing a generated output-voltage,

Em fiRl'z (14) a potential-transformer and negative phase-se- In Fig. 2, I also utilize 2 0 for energizing positive quence voltage-responsive networks E1 and E2, which may be of a conventional design.

For faults which are symmetrical with respect to phase-a, such as the faults represented in Figs. 1(b) to 1(e), the four phase-sequence networks I1, 12, E1 and E2, might simply be connected with proper polarities to form the relay operating quantity. However, for faults on other phases, the phase-angles would be incorrect to provide the same relay operating quantity for the same distance of the fault from the relay.

In order to obtain a response to the absolute values I1, I2, E1 and E2 of the phase-sequence quantities, I have shown a plurality of rectifier-bridges 23, 24, 25 and 26 associated with the respective phase-sequence networks I1, 12, E1 and E2, and the output-diagonals of these rectifier-bridges are illustrated as being connected in series with each other, in a relaying circuit 2-1, to produce a relaying voltage according to the equation,

Er=i1-ie-E'1+E2 (15) It will be noted that the voltages corresponding to T2 and E1 are reversed, with respect to the voltages corresponding to 11 and E2, in order to obtain a balance-point, corresponding to Er=0, which is the same as is obtained in Equation 8 by placing Z1=1.

The rectifier-bridges 23, 24, 25 and 26 are preferably made up of asymmetrically conducting rectifiers, which might be copper-oxide rectifiers or any equivalent rectifiers.

It will be noted that the rectifier-elements in the bridges 24 and 25, responding to I2 and E1, respectively, are directed so as to oppose the positive flow of current in response to the voltagecutputs of the other two rectifier-bridges 23 and 26. If the reverse-current impedances of the rectifier-bridges 24 and 25 are inconveniently large, these bridges may be shunted by impedances 28 and 29, respectively, so as to produce a voltage-drop of the proper amount, when current is flowing in the relaying circuit in the positive direction as determined by the other two rectifier-bridges 23 and 26.

The relaying circuit 21, which responds according to Equation 15, is utilized to energize a direct-current relay 3% having a contact-member 3| which is utilized to control the energization of the tripping coil [3 of the circuit-breaker 9. This relay 30 may advantageously be of the polarized type, as shown, so as to obtain an operating force which varies as the first power of the impressed relaying voltage Er, rather than varying as the square of the impressed voltage, as in other types of relays. The first-power response minimizes the departure of the operating point from the theoretically correct balancepoint of the relay, the operating point being the actual line-circuit conditions at which the relaying-voltage Er becomes large enough to overcome the restraint of the biasing spring 32 of the relay.

It will be noted that the rectifier-bridges 23 and 26 produce current in a direction tending to cause an operative response of the polarized relay 30, tending to move its contact-member 3| from its normal biased position to its tripping position. On the other hand, the voltages generated in the rectifier-bridges 24 and 25 tend to send current in the reverse direction, in the relaying circuit 21, thus tending to restrain the operation of the polarized relay 30, or to hold its contact-member 31 more strongly in its normal biased position.

If desired, the relaying circuit 21 may be provided with an additional rectifying means, 33, for interposing an additional impediment against current-flow in the negative or relay-restraining direction.

The rectifying means 24 and 25, which are associated with the phase-sequence filters/I2 and E1 are preferably of the full-Wave type, and are preferably provided with direct-current filters, symbolized by capacitors 34 and 35, connected across the output-terminals thereof, so as to smooth out the rectified voltage-wave to any desired extent, depending upon the necessary speed of relay-response and the necessary accuracy of the fault-distance measuring-operation. As a matter of convenience or expediency, I prefer to utilize similar full-wave rectifyingmeans, with similarly filtered outputs, for the other two rectifier-bridges 23 and 26, but these precautions are the most needed in connection with the two rectifier-bridges 24 and 25 which produce restraining voltages. If these restraining voltages were not substantially smoothtopped voltage-waves, the peaks in these voltages would vary in phase position according to the phase on which the fault Occurred on the protected line-section 5, and if the wave-forms of the relay-operating voltages produced in the rectifiers 23 and 26 were similarly peaked, the peaks would not always coincide to produce an accurate relaying response.

The outputs of the two current-responsive phase-sequence networks I1 and I2 are also preferably. associated with voltage-limiting means, such as a saturable transformer or reactancedevice 3?, and a space-discharge device such as a neon, or other gas-filled lamp 38, as described and claimed in a Bostwick application, Serial No. 182,980, filed January 3, 1938. The effect of these voltage-limiting devices3l and 38 is to produce a limited voltage of more nearly sinusoidal waveform than could be obtained with either device 37 or 38 alone, and this limited voltage is of a value higher than the relay operating-point, so that the voltage-limiting means 31 and 38 do not have any appreciable effect upon the balancepcint of the relay 38; For faults which are closer to the relaying point than the balance-point at which the relay 33 just barely operates, the line- -currents may be much larger, and the voltage limiting means 31 and 38 then come into play .to limit the maximum voltage Or current which has to be handled both by the rectifying-means 723 and 24, and by the operatin coil of the relay .30.

The voltage-filters E1 and E 2 have definite :maximum outputs, as distinguished from the very large, maximum outputs which are possible :in the case of the current-responsive filters I1 and I2, and hence these voltage-filters E1 and E2 will generally not require such limiting devices as the saturable transformer 31 and the neon lamp 38, although obviously they may be added, in certain situations where they may be advantageous.

It will be understood that the magnitudes of the voltage-output of the four rectifier-bridges 23, 24, 25 and 26, as expressed in Equation 15, may be adjusted by any convenient means, in order to adjust the balance-point and operating conditions of the relay 30.

In operation, if the fault on the transmission line is at any location between the relaying station, or circuit-breaker station 9, and the balance-point of the relay, corresponding to Equation 8 or 15, the net current-responsive relaying-voltages (I1-I2) will be in excess of the net voltage-responsive relaying-voltages (El-E2), and the right-hand side of Equation 15 will be greater than zero, with a resultant current-flow through the relay 30 in a relayoperating direction, producing a tripping-operation of the circuit-breaker 9, or producing any other desired control-action. For all faults beyond the relay balance-point, the relay-restraining voltages will predominate, tending to send current through the polarized relay 3!] in the restraining direction. This current in the restraining direction will be strictly limited, however, by reason of the asymmetrically conducting properties of the rectifiers 23, 2B and 33in the relaying circuit 21.

This relaying combination or system can be made fast in its operation, having a maximum operating time (at the balance-point) well under one cycle, assuming a (SO-cycle line 5. The operating time of the relay is much faster for faults which are close in, or adjacent to the relaying point 9. Furthermore, my relaying system produces a relay-operating force which is fairly steady throughout a cycle of the line-frequency current, a feature wherein it differs from previous fault-detecting arrangements which have given an indication, of the proper ratio, only at certain periods during the line-frequency cycle.

As previously pointed out, my relaying system provides very nearly the same measurement of distance from the relaying point to the fault, for any type of phase-fault, including three-phase faults, line-to-line faults, and double line-toground faults, and it reaches a shorter distance for ground-faults, which is another way of saying that it does not respond to ground-faults at or beyond the normal balance-point for phasefaults.

It is possible to add means, in addition to the relaying circuit 21, for causing the polarized relay 30 to respond to ground-faults at the same distance as the balance-point for phase-faults, or at any other desired ground-fault balancepoint. To this end, I show, in Fig.2, a switch 4| in the residual-current portion of the output circuit of the current-transformers l4, and I shunt this switch 4| with a resistor 42, so that, when the switch 4| is open, a voltage-drop is produced in the resistance 42, proportional to the value of the residual current (Ia+Ib+Ic)=3IO. The I0 voltage-drop in the resistor 42 is applied, through a voltage-limiting device 31 and 38', to a rectifier-bridge 43, the output-circuit 41 of which is connected in parallel-circuit relation to the phase-fault-responsive re1aying-circuit 27, so that the operating coil of the polarized relay 3!] is impressed with an operating voltage from either one of the two relaying circuits 2'! and 41, whichever voltage is the higher. The asymmetrically conducting properties of the rectifiers 23, 26, 33 and 43 prevent the two parallel-connected relaying circuits 2! and 41 from short-circuiting each other, so that the result of these two circuits is a direct-current relaying-voltage corresponding to the maximum voltage which one of the two circuits 21 and 41.

The relay circuit 41, which is responsive to the absolute value of the zero phase-sequence component of the line-current, produces a voltage 7610, thus making the polarized relay 30 a is produced in either ground-fault overcurrent relay, the setting of which may be altered by properly controlling the factor k. It will be understood that, when both relaying circuits 2'! and 41 are in operation, the relay 30 becomes a combined phase-impedance and ground-overcurrent relay of separately adjustable setting for phase-faults and for groundfaults, respectively.

Other forms of my invention, utilizing rectified single-phase quantities derived from phase sequence-components, which can be combined to derive a single unidirectional protective relaying quantity, are shown in my copending application Serial No. 338,093, filed May 31, 1940.

While I have illustrated my invention in a single preferred form of embodiment, it will be obvious that many changes may be made by those skilled in the art, without departing from the essential principles of my invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language and the prior art.

I claim asmy invention:

1. Protective relaying equipment for a threephase electrical apparatus, comprising means including rectifier-means, for deriving a first direct-current relay quantity selectively responsive to the absolute value of the positive phase-sequence current-component of the current in said apparatus, means including rectifier-means, for deriving a second direct-current relaying quantity selectively responsive to the absolute value of the negative phase-sequence curernt-component of the current in said apparatus, and relaymeans responsive, in some measure, to the difference between said first and second direct-current relaying quantities.

2. Protective relaying equipment for a threephase electrical apparatus comprising means for deriving a first relaying quantity I1 selectively responsive to the absolute value of the positive phase-sequence current-component of the current in said apparatus, means for deriving a second relaying quantity I2 selectively responsive to the absolute value of the negative phase-sequence current-component of the current in said apparatus, means for deriving a third relaying quantity E1 selectively responsive to the absolute value of the positive phase-sequence voltagecomponent of the voltage on said apparatus, means for deriving a fourth relaying quantity E2 selectively responsive to the absolute value of I the negative phase-sequence voltage-component of the voltage on said apparatus, and relaymeans responsive, in some measure, to the ratio of (I1I2) to (E1E2).

3. Protective relaying equiment for a threephase electrical apparatus, comprising means for deriving afirst relaying quantity I1 selectively responsive to the absolute value of the positive phase-sequence current-component of the current in said apparatus, means for deriving a second relaying quantity I2 selectively responsive to the absolute value of the negative phase-sequence current-component of the current in said app-aratus, means for deriving a third relaying quantity E1 selectively responsive to the absolute value of the positive phase-sequence voltage-component of the voltage on said apparatus, m eans for deriving a fourth relaying quantity E2 selectively responsive to the absolute value of the negative phase-sequence voltage-component of the voltage on said apparatus, and relay-means utilizing the quantities I1 and E2 to operate the relay and Beer AVAlLABLE COP,

utilizing the quantities I2 and E1 to restrain the relay.

4. Protective relaying equipment for a threephase electrical apparatus, comprising means for deriving a first relaying voltage I1 selectively responsive to the vector value of the positive phasesequence current-component of the current in said apparatus, means for deriving a second relaying voltage I2 selectively responsive to the vector value of the negative phase-sequence currentcomponent of the current in said apparatus, rec tifier-means for deriving a rectified voltage 11 from the voltage I1, rectifier-means for deriving approximately smooth-wave rectified voltage I2 from the voltage I2, and relay-means responsive, in some measure, to the difference between said rectified voltages I1 and I2.

5. Protective relaying equipment for a threephase electrical apparatus, comprising means for deriving a first relaying voltage I1 selectively responsive to the vector value of the positive phasesequence current-component of the current in said apparatus, means for deriving a second relaying voltage I2 selectively responsive to the vector value of the negative phase-sequence currentcompenent of the current in said apparatus, means for deriving a third relaying voltage E1 selectively responsive to the vector value of the positive phase-sequence voltage-component of the voltage on. said apparatus, means for deriving a fourth relaying voltage E2 selectively responsive to the vector value of the negative phase-sequence voltage component of the voltage on said apparatus, rectifier-means for deriving a rectified voltage I1 from the voltage I1, rectifier-means for deriving an approximately smooth-wave rectified voltage I2 from the voltage I1, rectifiermeans for deriving an approximately smooth- Wave recti ied voltage E1 from the voltage E1, .rec ifiewmea s f r deri n rectified volta e from the voltage and relay-means responsive, in some measure, to the ratio of (I1-I2) to a a 6. Protective relaying equipment for a threephese electrical apparatus. comprising means for deriving a first relayin voltage I1 selectively res onsive to the vector value of the positive phasesecuence ci1lrent-component of the current in said ap aratus. means for deriving a second relayin volta e I2 selectively responsive to the vect r value of the negative phase-sequence currentcnmnonent of the current in said apparatus, means for deriving a third relaying voltage E 1 selectiv lv r sponsive to the vector value of the KflSltlVQ phase-sequence voltage-component of the voltage on said a paratus, means for deriving a fourth relaying voltage E2 selectively responsive to the vector value of the negative phase-sequence voltage component of the voltage on said apparatus, rectifier means for deriving a rectified voltage I1 from the voltage I1, rectifier means for deriving an approximately smoothwave rectified voltage I2 from the voltage I2, rectifier-meansv for deriving an approximately smooth-wave rectified voltage E1 from the voltage E1, rectifier-means for deriving a rectified voltage E2 from the voltage E2, and relay-means utilizing the quantities I1 and E2 tooperate the relay and utilizing the quantities I2 and E1 to restrain the relay.

7. Protective relaying equipment for a threephase electrical apparatus, comprising means for deriving a first relaying voltage I1 selectively responsive to the vector value of the positive phasesequence current-component of the current in said apparatus, means for deriving a second relaying voltage I2 selectively responsive to the vector value of the negative phase-sequence current-' means for deriving an approximately smoothwave rectified voltage I2 from the voltage I2, rectifier means for deriving an approximately smooth-Wave rectified voltage E1 from the voltage E1, rectifier-means for deriving a rectified voltage E2 from the voltage E2, a direct-current relay, and electrical energizing-means for said direct-current relay, said electrical energizingmeans comprising an electrical en ergizing-circuit including said four voltages I1, I2, E1 and E2 in series-circuit relation to each other, with the voltages I2 and E1 reversed with respect to the voltages I1 and E2.

8. Protective relaying equipment for a threephase electrical apparatus, comprising means for deriving a first relaying voltage I1 selectively responsive to the vector value of the positive phase-sequence current-component of the current in said apparatus, means for deriving a second relaying voltage I2 selectively responsive to the vector value of the negative phase-sequence current-component of the current in said apparatus, means for deriving a third relaying voltage E1 selectively responsive to the vector value of the positive phase-sequence voltage-component of the voltage on said apparatus, means for deriving a fourth relaying voltage E2 selectively responsive to the vector value of the negative phase-sequence voltage component of the voltage on said apparatus, means for deriving a fifth relaying voltage I selectively responsive to the vector value of the residual current in said apparatus, asymmetrically conducting rectifier-means for deriving a rectified voltage I1 from the voltage I1, asymmetrically conducting rectifier-means for deriving an approximately smooth-wave rectifier voltage I2 from the voltage I2, asymmetrically conducting rectifier-means for deriving an approximately smooth-wave rectified voltage E1 from the voltage E1, asymmetrically conducting rectifier-means for deriving a rectified voltage E2 from the voltage E2, asymmetrically conducting rectifier-means for deriving a rectified voltage In from the voltage In, a direct-current relay, and electrical energizing means for said directcurrent relay, said electrical energizing-means comprising two electrical energizing-circuits connected in parallel-circuit relation to each other, one of said electrical energizing-circuits including said four voltages I1, I2, E1 and E2 in series-circuit relation to each other, with the voltages I2 and E1 reversed with respect to the voltages I1 and E2, and the other of said electrical energizing circuits including said rectified volte In.

9. The invention as defined in claim 4, characterized by said rectifier-means which are associated with the relaying voltages I and I comeEsT ai/AiLAeLE COPS 22,179

prising means for limiting the maximum values of the rectified voltages I1 and I2 to values corresponding to faults closer than the pick-up point of the relay.

10. The invention as defined in claim 5, characterized by said rectifier-means which are associated with the relaying voltages I1 and I2 comprising means for limiting the maximum values of the rectified voltages I1 and I2 to values corresponding to faults closer than the pick-up point of the relay.

11. The invention as defined in claim 6, characterized by said rectifier-means which are associated with the relaying voltages I1 and I2 comprising means for limiting the maximum values of the rectified voltages I1 and I2 to values corresponding to faults closer than the pick-up point of the relay.

12. The invention as defined in claim 7, characterized by said rectifier-means which are associated with the relaying voltages I1 and I2 comprising means for limiting the maximum values of the rectified voltages I1 and I2 to values corresponding to faults closer than the pick-up point of the relay.

13. The invention as defined in claim 8, characterized by said rectifier-means which are associated with the relay voltages I1, I2 and I0 comprising means for limiting the maximum values to the rectified voltages I1, I2 and I0 to values-corresponding to faults closer than the pick-up point of the relay.

14. The invention as defined in claim '7, characterized by said electrical energizing-circuit including impedancemeansshunting the voltages I2 and E1, respectively.

15. The invention as defined in claim 8, characterized by the first-mentioned one of said electrical energizing-circuits including impedance-means shunting the voltages I2 and E1, respectively.

16. Protective relaying equipment for a polyphase electrical apparatus, comprising currentresponsive relaying-means for deriving an alternating-current relay-quantity which is selectively responsive to a residual current in said protected apparatus, rectifier-means associated with said current-responsive relaying-means for deriving a direct-current relaying-quantity which is se lectively responsive to the absolute value of the residual current in said apparatus, and a discriminatory fault-detecting direct-current relayingmeans associated with said rectifier-means so as to be responsive, in some manner, to the attainment of a predetermined absolute magnitude of a unidirectional electrical output-quantity of said rectifier-means for aifording a selective response to a predetermined fault-condition involving a predetermined residual current in said apparatus, said rectifier-means comprising means' for limiting the maximum value of said unidirectional electrical output-quantity after it has attained a value larger than the pick-up point of said discriminatory fault-detecting direct-current relaying-means.

17. Protective relaying equipment for a threephase electrical apparatus, comprising phasesequence-responsive means for obtaining a unidirectional selective responsive to the absolute value of the positive phase-sequence currentcomponent of the current in said apparatus substantially regardless of the time-phase or reversals of the alternating-current half-waves of opposite directions of current-flow of the alternating vector or wave-form of said positive phasesequence current-component, phase-sequence-responsive means for obtaining a unidirectional selective response to the absolute value of the negative phase-sequence current-component of the current in said apparatus substantially regardless of the time-phase or reversals of the alternating-current half-waves of opposite directions of current-flow of the alternating vector or waveform of said negative phase-sequence currentcomponent, and totalizing relaying-means responsive, in some measure, to both of uni directional selective responses.

18. Protective relaying equipment for a threephase electrical apparatus, comprising means, including rectifier-means, for deriving a first di rect-current relaying-quantity selectively responsive to the absolute value of the positive phasesequence current-component of the current in said apparatus, means, including rectifier-means,

phase electrical apparatus, comprising a first electro-responsive relaying-means for deriving an alternating-current relaying-quantity which is selectively responsive, in some manner, to a predetermined electrical-quantity-function of said protected apparatus for responding, in some manner, to a predetermined kind of fault in said protected apparatus, a second electro-respon'sive relaying-means for deriving an alternating-current relaying-quantity which is selectively responsive, in some manner, to another predetermined electrical-quantity-function of said protected apparatus for responding, in some manner, to a different predetermined kind of fault in said protected apparatus, a rectifier-means associated with each of said current-responsive relay-- ing-means each deriving a direct-current relaying-quantity which is selectively responsive, in some manner, to the absolute value of the alternating-current relaying-quantity derived by its associated electro-responsive relaying-means, circult-means including both of said direct-current relaying-quantities in series-circuit relation to each other, and a discriminatory fault-detectin direct-current relaying-means energized from said circuit-means for detecting the attainment of a predetermined absolute magnitude in an electrical quantity of said circuit-means.

20. A three-phase device having a three-phase line, a set of current transformers for said line, networks connected to said transformers comprising a plurality of means including impedance devices and circuits having three distinct pairs of connections for obtaining, respectively, across said pairs of connections, unidirectional sequencevoltages individually representative of the positive-sequence, negative-sequence, and zero-sequence components of the line-currents, and means for combining said sequence-voltages in a predetermined manner or manners for obtaining a response to line-conditions.

21. A three-phase device having a three-phase line, current transformers for said line, networks connected to said transformers comprising a plurality of means including impedance devices and circuits having three pairs of connections for obtaining across said pairs of connections, a plurality of sequence-voltages representative of the positive-sequence, negative-sequence, and zero-sequence components of the line-currents, and means including rectifiers for rectifying and combining said sequence-voltages.

22. Means for utilizing a single relay to respond to any one of a plurality of different kinds of faults in a three-phase electrical device to be protected, comprising the combination, with said relay, of selective phase-Sequence filter means energized by electrical quantities representative of electrical conditions in said electrical device, and circuit means from said selective phase-sequence filter means to said relay for energizing said relay with a current corresponding, in a predetermined manner or manners, to values, including scalar values, of a combination of rectifled, weighted, sequence-component electrical quantities derived individually by said phase-sequence filter means from the said electrical quantities in the protected device.

23. An electrical system responsive to the line currents in a three-phase device, comprising a plurality of network means for obtaining electrical quantities 6010, 70111, and kale, where 10, I1, and I2 are the zero-, positive-, and negativesequence components of the line-currents, and k0, 701, and R2 are selected constants, and means including a utilization circuit, for rectifying said quantities to obtain scalar values of each, and combining said scalar values in a predetermined manner or manners to obtain a single unidirectional electrical quantity utilizable as a discriminating function in said utilization circuit.

24. A three-phase device, network means for deriving individual single-phase electrical quantities representative, respectively, of negative and positive sequence-components of electrical quantities in said device, said network means having a plurality of pairs of junctions, one for each of said sequence-components, rectifier means connected to said junctions to convert said in dividual single-phase electrical quantities to individual unidirectional electrical quantities, and

a utilization circuit including the outputs of said rectifier means in series whereby said unidirectic-nal quantities are algebraically added.

25. A multi-phase device having a multi-phase circuit, means for obtaining eiectrical relaying quantities representative of electrical quantities in said circuit, said means comprising responsive means including device and circuits having a plurality f distinct pairs of connections for obtaining, across each of individual selected pairs of said connections, a voltage which is representative of a selected sequence--cornponent of said electrical quantities in said circuit, said responsive mean providing each of said selected pairs of connections with a voltage representative of a sequence-component different from that "oss another of said selected pairs of connections, means for obtaining individually rectified voltages from said representative voltages, and circuit means comprising means for combining the obtained rectified voltages, in a predetermined manner or manners, for obtaining a single relaying quantity having a unidirectional component.

26. A three-phase device having a three-phase circuit, means for obtaining electrical relaying quantities representative of electrical quantities in said circuit, said means comprising means including devices and circuits having three distinct pairs of connections for obtaining a voltage across one pair of said connections, which is representative of the positive-sequence component of said electrical quantities in said circuit, for obtaining a voltage across a second pair of said connections, which is representative of the negative-sequence component of said electrical quantities in said circuit, and for obtaining a voltage across a third pair of said pairs connections, which is representative of the zero-sequence component of said electrical quantities in said circuit, and means including rectifiers across said pairs of connections, said rectifiers having output connections.

2'7. The combination, with a three-phase device, of means for obtaining electrical quantities representative of electrical-conditions in said device, said means including impedance devices and circuits having three distinct pairs of connections for obtaining a sequence-voltage across one pair of said connections, which is representative of a positive-sequence component of said electrical-conditions in said device, for obtaining a sequence-voltage across a second pair of said connections, which is representative of a negative-sequence component of said electrical-conditions in said device, and for obtaining a sequence-voltage across a third pair of said connections, which is representative of a zero-sequence component of said electrical-conditions in said device, means including rectifiers across said connections, said rectifiers having output connections, circuit means including said rectifier output connections, for obtaining a single electrical quantity representative of a combination of sequence-voltages across said pairs of connections, and means responsive only to a predetermined value of said single electrical quantity.

28. The combination, with a polyphase electrical apparatus, of a first means for obtaining a first single-phase relaying quantity which is compositely responsive to a plurality of single-phase electrical quantities of said electrical apparatus, said composite response being in accordance with a first predetermined phase-sequence function, a second means for obtaining a second single-phase relaying quantity which is compositely responsive to a plurality of single-phase electrical quantities of said electrical apparatus, the last said composite response being in accordance with a second predetermined phase-sequence function, means for rectifying each of said single-phase relaying quantities, and means for obtaining a joint response to both of said rectified quantities.

29. The combination, with a polyphase electrical apparatus, of a plurality of different means for obtaining a plurality of different single-phase relaying quantities which are differently responsive, each to a plurality of electrical quantities of the polyphase electrical apparatus in accordance with a predetermined phase-sequence law of response, means for individually rectifying each of said single-phase relaying quantities, and means for obtaining a joint response to said rectified quantities.

30. The combination, with a polyp-hase electrical apparatus, of a plurality of different means for producing a plurality of different single-phase relaying quantities responsive to difierent phase sequence components of a predetermined electrical condition of said polyphase electrical appa-.

ratus, some of said single-phase relaying quantities being selectively responsive substantially exclusively respectively to a plurality of different rotational phase-sequence quantities, and at least one other of said single-phase relaying quantities being responsive to a zero phase-sequence quantity, separate means for individually rectifying the several single-phase relaying quantities. means for serially combining the rectified singlephase relaying quantities responsive to the rotational phase-sequence quantities, and means for parallelly combining the rectified singlephase relaying quantity responsive to the zero phase-sequence quantity with the resultant of the serial combination of the rectified single-phase relaying quantities responsive to rotational phase-sequence quantities, for obtaining a joint response dependent upon the rectified quantities.

31. An electrical system responsive to the electrical quantities in a multi-phase device, comprising a plurality of means for obtaining electrical quantitie koO, kiP, and kzN, where O, P, and N are the zero-, positive-, and negative-sequence components of the said electrical quantities, and k0, in, R2 are selected constants, and means including a utilization circuit, for rectifying said quantities to obtain scalar values of each, and combining said scalar values in a predetermined manner or manners to obtain a single unidirectional electrical quantity utilizable for a discriminating function in said utilization circuit.

32. A three-phase device having a three-phase line, means for deriving individual single-phase electrical quantities representative, respectively, of positive and negative sequence-components of voltage and of current quantities in said line, said means having a plurality of pairs of junctions, one for each of said sequence-components, rectifier means connected to said junctions to convert said individual single-phase electrical quantities to individual unidirectional electrical quantities, and a utilization circuit including the outputs of said rectifier means in series whereby said unidirectional quantities are algebraically added.

, EDWIN L. HARDER. 

